Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of the first image in a sequence of a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a second image thereof; and,

FIG. 3 is a third image thereof.

The outer broken lines in the figures show a display screen or portion thereof and form no part of the claimed design. The remainder of the broken lines in the figures show portions of the graphical user interface and form no part of the claimed design.

The appearance of the transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-3. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 